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<h1><a class="toc-backref" href="./changes-in-boost-1-32-0.html#id67" name="numeric-metafunction">Numeric Metafunction Protocol/Infrastructure</a></h1>
<p>The arithmetic, comparison and bitwise metafunctions are now
<cite>polymorphic</cite>, and can operate on a variety of numeric types,
including rational, fixed-point and complex numbers.  They allow
<cite>mixed arithmetic</cite>, meaning that you can perform an operation on
arguments of different types, and the result will yield the
largest/most general of the argument types. The infrastructure
allows user-defined numeric types to be freely intermixed with
predefined library types. See
<a class="reference" href="../../test/numeric_ops.cpp" target="_top">libs/mpl/test/numeric_ops.cpp</a>
for an illustrative example, and the <a class="reference" href="./reference-manual.html">reference manual</a> for
the formal infrastructure specification.</p>
<p>If you were using MPL numeric metafunctions on your own integral
wrapper class similar to <tt class="literal"><span class="pre">mpl::int_</span></tt>, you can plug your class
into the new infrastructure by extending it with the following
member:</p>
<pre class="literal-block">
typedef mpl::integral_c_tag tag;
</pre>
<p>For example:</p>
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<tr><td><pre class="first last literal-block">
template&lt; int n &gt; struct my_int
{
    static int const value = n;
    typedef my_int type;
};
</pre>
</td>
<td><pre class="first last literal-block">
template&lt; int n &gt; struct my_int
{
    <strong>typedef mpl::integral_c_tag tag;</strong>
    static int const value = n;
    typedef my_int type;
};
</pre>
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